ON THE NEAR-INFRARED MAGNETO-OPTICAL PROPERTIES OF FE-4+ IONS IN YTTRIUM IRON-GARNET

Calcium doped Yttrium Iron Garnet (YIG:Ca) films, because of their broadband optical absorption and birefringence in the near infrared, are of interest for the fabrication of magneto-optical isolators made of multilayer garnet films. In this paper we study in detail the Faraday rotation and magnetic circular dichroism associated with the optical transitions occurring in the 'two types' of Fe**4** plus centers previously identified in YIG:Ca. The spectra of type I centers result from the superposition of two transitions, both having paramagnetic character, at lambda equals 0. 92 and lambda equals 1. 57 mu m, while the spectra of type II centers exhibit two diamagnetic transitions at lambda equals 0. 95 and lambda equals 1. 16 mu m. The implications of these results for the understanding of the different nature of the two centers are discussed.